Preparation of a silica-alumina cracking catalyst



verting hydrocarbons and a catalyst therefor.

PREPARATION OF A SILICA-ALUMINA CRACKING CATALYST James A. Dinwiddie and Max A. Mosesman, Baytown,

Application March 6, 1953, Serial No. 340,891 6 Claims. (Cl. 252-463) The present invention is directed to a method for con- More particularly,'the invention is directed to the cracking of hydrocarbons in contact with an improved catalyst. more specific aspects the invention is concerned with an improved silica-alumina catalyst and a method for using same.

This application is a continuation-in-part of Serial No.

In its 318,213, filed November 1, 1952, for James A. Dinwiddie 1 and Max A. Mosesman and entitled Preparation of Improved Alumina.

The present invention may be briefly described as a catalyst composition comprising silica and alumina derived from boehmite.

The invention also includes a method for converting hydrocarbons which comprises contacting a heated hydrocarbon at a temperature in the range between 800 I and 1200" F. with a catalyst comprising silica and alumina derived from boehmite for a length of time suf-' ficient to crack the hydrocarbon and to form a product having improved properties.

The alumina forming a part of the improved catalyst is derived from boehmite, which is a monohydrate of alumina. The boehmite is produced by controlled hydrolysis of aluminum alcoholate. The controlled hydrolysis is effected by subjecting an alcoholate of aluminum, such as an alcoholate formed by reacting aluminum turnings with an aliphatic alcohol having from 1 to 10 carbon atoms, to contact with atmospheric moisture at" atmospheric conditions of temperature and pressure to form boehmite.

The alcohols employed in forming the alcoholate may suitably be methyl, ethyl, propyl, butyl, amyl, hexyl,

heptyl, octyl, nonyl or decyl alcohols but preferably is an alcohol having from about 5 to 8 carbon atoms. The aluminum metal is reacted with the alcohol at a temperature in the range between 75 and 300 F.

Although it is preferred that the hydrolysis operation be conducted with atmospheric moisture, such as air having a relative humidity of from 20 to 100 percent, the hyof an alcohol soluble and hydrolyzable organic compound of silicon with the aluminum alcoholate prior to hydrolysis of the latter. As examples of the organic compounds of silicon may be mentioned ethyl, propyl, butyl,

amyl, and phenyl ortho silicates and the like; silicon tetrachloride and other halides of silicon such as silicon bromide, iodide, fluoride, and the like, may also be used.

The amount of the compound of silicon employed should be selected to provide a finished catalyst comprising between 95 and 50 mole percent of silica and between 2,775,562 Patented Dec. 25, 1956 5 and 50 mole percent of alumina derived from boehmite. Desirable results in converting hydrocarbons may be obtained with a catalyst comprising approximately 10 mole percent of alumina derived from boehmite and approximately mole percent of silica. .It is desirable that in no case the amount of alumina derived from boehmite should exceed equimolar amounts of the catalyst and in no case the amount of silica should be less than equimolar amounts of the catalyst. I

In employing the catalyst of the present invention in converting hydrocarbons temperatures in the range from 800 to 1200 F. should be employed. Desirable results may be obtained at temperatures between 850 to 950 F.

The operation may be conducted in either a fixed bed or fluidized type of operation. When the operation is in a fixed bed the catalyst, such as described before, may be arranged in a reaction chamber as a vertical bed and the heated hydrocarbon in a vaporous condition allowed to pass therethrough to contact the catalyst intimately for a suflicient length of time to convert the hydrocarbon or to crack it to more desirable products.

When the operation is of the fluidized powder type the heated hydrocarbon in a vaporous condition has the catalyst comprising silica and alumina derived from boehmite suspended in the vaporous hydrocarbon and allowed to contact same as a suspension for a sufiicient length of time to crack the heated hydrocarbon. When a fluidized powder type operation is employed, the catalyst of the present invention should be of suitable particle sizes to allow it to be readily suspended in the vaporous hydrocarbon; thus the catalyst may suitably have particle diameters ranging from 0 to 100 microns with the greater portion of the catalyst having particle diameters in the range from about 20 toabout 80 microns. Catalyst particles having these diameters may be readily suspended in vaporized hydrocarbons and employed in the fluidized powder technique.

When the catalyst of the present invention is employed in fixed bed operations it may suitably be formed into pills and arranged in either a vertical or horizontal. bed and the hydrocarbons passed in contact therewith. i

A suitable catalyst may be prepared by adding ethy orthosilicate, which may or may not be dissolved in normal amyl alcohol, to aluminum amylate in normal amyl alcohol followed by atmospheric hydrolysis by contacting with moisture from the atmosphere under atmospheric conditions of temperature and pressure. Thus a catalyst comprising of silica and 5% of aluminarderived from boehmite may be formed by this method.

The invention will, be further illustrated by reference to the drawing in which the single figure presents a flow diagram of one preferred mode of operation employing the catalyst of the present invention.

Referring now to the drawing, numeral 11 designates a charge tank in which a feed hydrocarbon, such as a gas oil, is provided from a source not shown. The gas oil is introduced into the system by line 12 containing pump 13 and is pumped into a heater or furnace 14 containing a coil 15. Furnace 14 is provided with heating means, not shown, which serves to raise the temperature of the hydrocarbons passing through coil 15 to a temperature in the range from 800 to 1200 F. and to vaporize the hydrocarbons. The heated and vaporized hydrocarbons issue from furnace 14 by way of line 16 and pass into a fixed bed reaction zone 17 containing a bed of catalyst 18 such as silica and alumina derived from boehmite formed in the manner which has been described. On contact of the heated and vaporous hydrocarbons with the bed 18 for a sufficient length of time the hydrocarbons are converted or cracked to more desirable products. These products issue from reaction 1 catalyst. alcohol mixture orsolution is then hydrolyzed by contact zone 17 byline 19 and vpassintoa coolerorcondenserlo containing a cooling coil 21 wherein the hydrocarbons are cooled to a temperature below the reaction temperature:by circulationiof water through cooling zone 20 by lines- 22. and 23.

The cooledhydrocarbonspreferably at a distillation temperature arewithdrawn from cooler 20 by line 24 and-discharged thereby into a fractionation zone 25 which isshownsasra singledistillation tower orwhich may be a pluralitypof distillationtowers, each'equipped with all facilities necessary to provide fractional distillation. Zone 25 may suitably include flashvaporization equipment as desired. Thus zone 25i is i intended to include suitable internal:vapor-liquid contacting means, such-as bell cap trays,.packingzandthe like, means for inducing reflux, condensers-1 and-the like; Zone ZS'is provided with line 26 for removing light overhead fractions and with lines 27; 28 and 29 controlled, respectively, by valves 30, 31 and:32.'by way'of which the desirable products may be removedii asside streams. Heavier fractions may be withdrawn: by line '33;

Conditions may be adjusted in zone 25 by heating means: illustrated by steam coil 34.

From the foregoing discussion taken with'the drawing it willbeseen'thatthe present invention is applicable to a..simple:'processfor converting hydrocarbons to more desirablerproducts;

In order to. illustrate-theinvention further the desired quantity of ethyl orthosilicate is added to a given quantity of aluminumalcoholate in n-amyl alcohol; the amount of ethyl orthosilicate is selected to provide the desired concentration ofsilica and gamma alumina in the finished The aluminum alcoholate-ethyl orthosilicatewith tatmosphericmoisture having a' relative humidity of from 20 to -'l00- percent 'at'atmospheric temperature. The precipitate .from' thehydrolysisoperation is then filtered, dried. atf230 R, which may include drying in vacuo, pilledandcalcined'iinair atia-temperature of 800 to 1200 F. for 3 to 6 hours. After the calcination operation; the catalyst is suitable. for use in fixed bed cracking hydrocarbons.

The:catalyst alternatively may-be prepared by adding the desiredquantity ofethyl orthosilicate to a given amount of boehmite prepared by the prior hydrolysis ofzthe aluminum alcoholate. This admixture, after by drolysis of the :addedethyl orthosilicate by atmospheric 'moisture is then subjected to the usual drying, pilling,

and 2 activationtreatments described above. Similarly, silicon tetrachloride may be employed in each of the instances inlieuof ethyl orthosilicate. X-ray diffraction patterns of catalysts produced, as has been described, indicate the finished catalyst to lie-amorphous.

Ifiitl*is*desired. to' employ the catalyst in a fluidized powderoperation, the calcined catalyst is ground. and adjusted to the proper particle size distribution in the range given before.

Although the. invention has been described with respect to drying the filtered precipitate by heating, it is contemplated that spray techniques may be employed to accomplish the same result.

Although gas oil hydrocarbons may form the preferred feed stock when the improved catalyst is used in cracking hydrocarbons, it is contemplated that other hydrocarbons may be used. For example, hydrocarbons boiling from about 400 to about 1000 F. may suitably be converted employing the catalyst'of the present invention. It is contemplated that distillatehydrocarbonsfrom crude petroleum as well as residual crude petroleum fractions maybe used as feed stocks. Thus petroleum fractions constituting the heavier portions of crude petroleums may be suitably contactedwiththe improved silica and gamma alumina catalyst and converted into useful hydrocarbons;

The nature and objects of the present invention having been completely describedand illustrated, what we wish to-claimas new and useful and to secure by Letters Patent is:

l. A method for producing a heat stable-catalyst suitable for converting hydrocarbons which comprises admixing an alcohol soluble and hydrolyzable silicon compound with aluminum alcoholate, hydrolyzing the admixture by contacting same with water vapor to form a precipitate of said silicon compound-and boehmite, drying the precipitate and calcining the dried precipitate at asuificiently high temperature to form a heat stable catalyst comprising silica and alumina- 2. A method in accordance with claim 1 in which the silicon compound is ethyl orthosilicate.

3. A method in accordance with claim 1 in which the silicon compound is a silicon halide.

4. A method in accordance with claim 1 in which the Water vapor is moisture-laden 'air.

5. A methodin accordance with claim 1 in which the water vapor is steam.

6. A method for preparing a heat stable catalyst suitable for cracking operations which comprises incorporating silica with hoehmite' prepared by prior vaporized Water hydrolysis of an'aluminum alcoholate prepared by reacting. aluminum with analiphatic alcohol having 1 to 10 carbon atoms in the molecule to form an admixture and then heating the admixture to a temperature in the range/between 800 and 1200 F. in the presence of air to obtain a silica and alumina catalyst.

References Cited in'thefile of this patent UNITED STATES'PATENTS 2,317,803 Reeves et al. Apr. 27, 1943 2,636,865 Kimberlin Apr. 28, 1954 2,749,216 Dinwidd'ie et a1 June 5, 1956 FOREIGN PATENTS 667,145 Great Britain Feb. 27, 1952 

1. A METHOD FOR PRODUCING A HEAT STABLE CATALYST SUITABLE FOR CONVERTING HYDROCARBONS WHICH COMPRISES ADMIXING AN ALCOHOL SOLUBLE AND HYDROLYZABLE SILICON COMPOUND WITH ALUMINUM ALCOHOLATE, HYDROLYZING THE ADMIXTURE BY CONTACTING SAME WITH WATER VAPOR TO FORM A PRECIPITATE OF SAID SILICON COMPOUND AND BOEHMITE, DRYING THE PRECIPITATE AND CALCINING THE DRIED PRECIPITATE AT A SUFFICIENTLY HIGH TEMPERATURE TO FORM A HEAT STABLE CATALYST COMPRISING SILCIA AND ALUMINA. 